Britain’s border controls will come down over the course of this century, John McDonnell said.

The Shadow Chancellor said it was “inevitable” that countries would have to open their borders.

“We are seeing it in Europe already. The movement of peoples across the globe will mean that borders are almost going to become irrelevant by the end of this century so we should be preparing for that and explaining why people move,” he told the BBC’s Sunday Politics show.

Mr McDonnell said he expected borders to come down by the end of this century.

“We’re seeing people ignoring borders already as they fly from Syria, so therefore what we should be doing is making sure that if there’s no forced movement look at the push and pull factors and we ensure that we have as I say, conflict prevention, tackling of inequality and also policies that tackle climate change.

“What I’m saying is is that if you look at all the analysis of what’s happening over the next, well 75 years, this century, what will happen the movement of people as much that borders are very difficult to maintain and that will happen by the end of this century. We should be opening up the debate of how we handle that and one of the issues that we have to tackle is why people are moving and it is about conflict, it is about climate change,” he said.

The Shadow Chancellor also said Britain should take its “fair share” of the 4 million migrants displaced by the wars in Iraq, Libya and Syria . The Government has said it will accept 20,000 Syrian refugees from camps in Lebanon and Jordon between now and 2020.

But Mr McDonnell said the UK should not “stand on one side” while people suffer.

“I think we should be doing more in terms of assisting refugees coming from Syria and we should be doing more to take – I think those people who are in desperate need. People are drowning in the Mediterranean now,” he said.

Former shadow Home Secretary Yvette Cooper said she strongly disagreed with Mr McDonnell’s plans for open borders.

She said: “Border checks are really important for managing the refugee crisis - including stopping trafficking gangs, protecting child refugees who are disappearing in Europe, making sure proper asylum assessments take place so refugees get swift help and preventing people from travelling illegally if they are not refugees and have a safe home to return to.

“Labour needs to maintain a policy in favour of firm and effective border controls alongside help for refugees. I also disagree with John McDonnell about what will happen in the coming decades. Given the challenges we face, proper border checks are likely to become more important not less in future.”

Backlash: German Chancellor Angela Merkel has faced criticism over her country's open borders policy (Image: Getty)

Angela Merkel tried to fend off criticism of Germany’s open doors policy by saying migrants from Iraq and Syria would go home once their countries returned to peace.

The German leader has faced a backlash after more than 1million migrants were taken into the country last years.

She stressed they had only been given permission to stay for a limited period of time.

“We need...to say to people that this is a temporary residential status and we expect that once there is peace in Syria again, once IS has been defeated in Iraq, that you go back to your home country with the knowledge that you have gained,” she said.